/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context.support;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.util.StringUtils;

/**
 * (1) BeanDefinition的Resource定位 (2) BeanDefinition的载入和解析 (3) BeanDefinition的注册
 * 
 * Standalone XML application context, taking the context definition files from
 * the file system or from URLs, interpreting plain paths as relative file
 * system locations (e.g. "mydir/myfile.txt"). Useful for test harnesses as well
 * as for standalone environments.
 * 
 * <p>
 * <b>NOTE:</b> Plain paths will always be interpreted as relative to the
 * current VM working directory, even if they start with a slash. (This is
 * consistent with the semantics in a Servlet container.) <b>Use an explicit
 * "file:" prefix to enforce an absolute file path.</b>
 * 
 * <p>
 * The config location defaults can be overridden via
 * {@link #getConfigLocations}, Config locations can either denote concrete
 * files like "/myfiles/context.xml" or Ant-style patterns like
 * "/myfiles/*-context.xml" (see the
 * {@link org.springframework.util.AntPathMatcher} javadoc for pattern details).
 * 
 * <p>
 * Note: In case of multiple config locations, later bean definitions will
 * override ones defined in earlier loaded files. This can be leveraged to
 * deliberately override certain bean definitions via an extra XML file.
 * 
 * <p>
 * <b>This is a simple, one-stop shop convenience ApplicationContext. Consider
 * using the {@link GenericApplicationContext} class in combination with an
 * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader} for
 * more flexible context setup.</b>
 * 
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #getResource
 * @see #getResourceByPath
 * @see GenericApplicationContext
 */
public class FileSystemXmlApplicationContext extends AbstractXmlApplicationContext {

	private String[] configLocations;

	/**
	 * Create a new FileSystemXmlApplicationContext, loading the definitions
	 * from the given XML file and automatically refreshing the context.
	 * 
	 * @param configLocation
	 *            file path
	 * @throws BeansException
	 *             if context creation failed
	 */
	public FileSystemXmlApplicationContext(String configLocation) throws BeansException {
		this(new String[] { configLocation }, true, null);
	}

	/**
	 * Create a new FileSystemXmlApplicationContext, loading the definitions
	 * from the given XML files and automatically refreshing the context.
	 * 
	 * @param configLocations
	 *            array of file paths
	 * @throws BeansException
	 *             if context creation failed
	 */
	public FileSystemXmlApplicationContext(String[] configLocations)
			throws BeansException {
		this(configLocations, true, null);
	}

	/**
	 * Create a new FileSystemXmlApplicationContext with the given parent,
	 * loading the definitions from the given XML files and automatically
	 * refreshing the context.
	 * 
	 * @param configLocations
	 *            array of file paths
	 * @param parent
	 *            the parent context
	 * @throws BeansException
	 *             if context creation failed
	 */
	public FileSystemXmlApplicationContext(String[] configLocations,
			ApplicationContext parent) throws BeansException {
		this(configLocations, true, parent);
	}

	/**
	 * Create a new FileSystemXmlApplicationContext, loading the definitions
	 * from the given XML files.
	 * 
	 * @param configLocations
	 *            array of file paths
	 * @param refresh
	 *            whether to automatically refresh the context, loading all bean
	 *            definitions and creating all singletons. Alternatively, call
	 *            refresh manually after further configuring the context.
	 * @throws BeansException
	 *             if context creation failed
	 * @see #refresh()
	 */
	public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh)
			throws BeansException {
		this(configLocations, refresh, null);
	}

	/**
	 * Create a new FileSystemXmlApplicationContext with the given parent,
	 * loading the definitions from the given XML files.
	 * 
	 * @param configLocations
	 *            array of file paths
	 * @param refresh
	 *            whether to automatically refresh the context, loading all bean
	 *            definitions and creating all singletons. Alternatively, call
	 *            refresh manually after further configuring the context.
	 * @param parent
	 *            the parent context
	 * @throws BeansException
	 *             if context creation failed
	 * @see #refresh()
	 */
	public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh,
			ApplicationContext parent) throws BeansException {

		super(parent);
		// (1)设置BeanDefinition的配置文件的路径，使得所有在配置文件中的BeanDefinition都能得到有效地处理
		this.configLocations = StringUtils.trimArrayElements(configLocations);
		// (2)通过refresh()方法启动了IoC容器的初始化
		if (refresh) {
			refresh();
		}
	}

	protected String[] getConfigLocations() {
		return this.configLocations;
	}

	/**
	 * Resolve resource paths as file system paths.
	 * <p>
	 * Note: Even if a given path starts with a slash, it will get interpreted
	 * as relative to the current VM working directory. This is consistent with
	 * the semantics in a Servlet container.
	 * 
	 * @param path
	 *            path to the resource
	 * @return Resource handle
	 * @see org.springframework.web.context.support.XmlWebApplicationContext#getResourceByPath
	 */
	protected Resource getResourceByPath(String path) {
		if (path != null && path.startsWith("/")) {
			path = path.substring(1);
		}
		return new FileSystemResource(path);
	}

}
